if i uninstall thunderbird and reinstall it, will I lose my saved emails?

Normally, no, you won't lose it. Your saved emails and preferences are stored in a separate location (called the "Profile",) than the program itself, and reinstalling the program usually doesn't touch it. However, in the computer world things can go wrong when you least expect it, so it's best practice to make a backup copy of the Profile before re-installing or making other significant changes to Thunderbird. Here's an article explaining how to do that: https://kb.mozillazine.org/Profile_backup#Manually_back_up_the_profile